Multimodal polypropylene composition for pipe applications

Abstract

A multimodal propylene copolymer composition suitable for pipe applications comprising a multimodal propylene copolymer (U) with at least one comonomer selected from alpha-olefins with 2 or 4 to 8 carbon atoms in a total amount of 4.0 to 10.0 mole-%, wherein the composition has a melt flow rate MFR2 (2.16 kg, 230° C.) of 0.05 to 1.00 g/10 min determined according to ISO 1 133, a content of xylene cold solubles (XCS) of 4.0 to 17.0 wt.-% determined at 25° C. according to ISO 16152, and a poly dispersity index PI of 2.5 to 4.0 Pa−1 determined by rheological measurements according to ISO 6721-1 and ISO 6721-10.

The invention claimed is: 
     
       1. A multimodal polypropylene composition suitable for pipe applications, comprising:
 a multimodal propylene copolymer (U) that comprises: 
 (A) from 88 to 95 wt.-% of a propylene random copolymer composition (X) which comprises:
 i. from 30 to 60 wt.-% of a first propylene homopolymer or random copolymer (V) having an MFR 2  of from 0.3 to 5.0 g/10 min: and 
 ii. from 40 to 70 wt.-% of a second propylene homopolymer or random copolymer (W), having an MFR 2  of from 0.04 to 0.60 g/10 min; 
 iii. provided that at least one of said first propylene homopolymer or random copolymer (V) and said second propylene homopolymer or random copolymer (W) is a propylene random copolymer; and 
 
 (B) from 5 to 12 wt.-% of a propylene copolymer (Y) having a content of comonomer units of from 9.0 to 40.0 mole-%, wherein the comonomer is selected from at least one of the group consisting of ethylene and C 4 -C 8  alpha-olefins; 
 (C) wherein the multimodal propylene copolymer (U) has at least one comonomer selected from alpha-olefins with 2 or 4 to 8 carbon atoms in a total amount of 4.0 to 10.0 mole-%; 
 wherein the multimodal polypropylene composition has:
 i. a melt flow rate MFR 2  (2.16 kg, 230° C.) of 0.05 to 1.00 g/10 min determined according to ISO 1133; 
 ii. a content of xylene cold solubles (XCS) of 4.0 to 17.0 wt.-% determined at 25° C. according to ISO 16152; and 
 iii. a polydispersity index PI of 2.5 to 4.0 Pa −1  determined by rheological measurements according to ISO 6721-1 and ISO 6721-10. 
 
 
     
     
       2. The multimodal polypropylene composition according to  claim 1 , wherein the propylene copolymer (Y) has a melt flow rate MFR 2  of 0.0001 to 0.1 g/10 min. 
     
     
       3. The multimodal polypropylene composition according to  claim 1 , wherein:
 the first propylene random copolymer (V) has a content of comonomer units of from 1.0 to 6.0 mole-%; and 
 the second propylene random copolymer (W) has a content of comonomer units of from 3.0 to 12.0 mole-%. 
 
     
     
       4. The multimodal polypropylene composition according to  claim 1 , wherein the MFR 2  of the first propylene homopolymer or random copolymer (V) is higher than the MFR 2  of the second propylene homopolymer or random copolymer (W) and the MFR 2  of the second propylene homo polymer or random copolymer (W) is higher than the MFR 2  of the propylene copolymer (Y). 
     
     
       5. The multimodal polypropylene composition according to  claim 1 , further comprising from 0.1 to 10000 ppm by weight of a nucleating agent (Z). 
     
     
       6. The multimodal propylene copolymer composition according to  claim 5 , wherein the nucleating agent (Z) is a polymeric nucleating agent. 
     
     
       7. The multimodal polypropylene composition according to  claim 5 , wherein the polymeric nucleating agent is a polymer of vinylcyclohexane and/or 3-methyl-1-butene. 
     
     
       8. The multimodal polymer composition according to  claim 5 , wherein the polymeric nucleating agent (Z) is a polymer of at least one vinyl compound according to one of formulas (1) and (2):
   CH 2 ═CH—CHR 1 R 2   (1)
 
 wherein R 1  and R 2  together form a 5- or 6-membered saturated, unsaturated or aromatic ring that optionally contains substituents, or independently represent an alkyl group comprising 1 to 4 carbon atoms;
   CH 2 ═CH—CR 1 R 2   (2)
 
 
 wherein R 1  and R 2  together form a 5- or 6-membered aromatic ring that optionally contains substituents. 
 
     
     
       9. The multimodal polypropylene composition according to  claim 1 , wherein the relationship: crystallization temperature TC×comonomer content of the multimodal propylene copolymer (U) [° C. mole-%] is at least 400° C. mole-%. 
     
     
       10. The multimodal polypropylene composition according to  claim 1 , which has a Charpy Notched Impact Strength at 0° C. of at least 4.0 kJ/m 2 , determined according to ISO 179/1eA:2000 using notched injection moulded specimens. 
     
     
       11. The multimodal polypropylene composition according  claim 1 , which has a flexural modulus of at least 700 MPa, determined according to ISO 178 at a test speed of 2 mm/min and a force of 100 N on test specimens having a dimension of 80×10×4.0 mm 3  (length×width×thickness) prepared by injection moulding according to EN ISO 1873-2. 
     
     
       12. The multimodal polypropylene composition according to  claim 1 , which has a Charpy Notched Impact Strength at 0° C. of at least 5.0 kJ/m 2 , determined according to ISO 179/1eA:2000 using notched injection moulded specimens. 
     
     
       13. The multimodal polypropylene composition according to  claim 1 , which has a Charpy Notched Impact Strength at 0° C. of at least 6.0 kJ/m 2 , determined according to ISO 179/1eA:2000 using notched injection moulded specimens. 
     
     
       14. The multimodal polypropylene composition according to  claim 1 , which has a Charpy Notched Impact Strength at 0° C. of at least 7.0 kJ/m 2 , determined according to ISO 179/1eA:2000 using notched injection moulded specimens. 
     
     
       15. The multimodal polypropylene composition according to  claim 1 , which has a Charpy Notched Impact Strength at 0° C. of 8.0 to 40 kJ/m 2 , determined according to ISO 179/1eA:2000 using notched injection moulded specimens. 
     
     
       16. The multimodal polypropylene composition according  claim 1 , which has a flexural modulus of at least 750 MPa, determined according to ISO 178 at a test speed of 2 mm/min and a force of 100 N on test specimens having a dimension of 80×10×4.0 mm 3  (length×width×thickness) prepared by injection moulding according to EN ISO 1873-2. 
     
     
       17. The multimodal polypropylene composition according  claim 1 , which has a flexural modulus of at least 800 MPa, determined according to ISO 178 at a test speed of 2 mm/min and a force of 100 N on test specimens having a dimension of 80×10×4.0 mm 3  (length×width×thickness) prepared by injection moulding according to EN ISO 1873-2. 
     
     
       18. The multimodal polypropylene composition according  claim 1 , which has a flexural modulus of at least 830 MPa, determined according to ISO 178 at a test speed of 2 mm/min and a force of 100 N on test specimens having a dimension of 80×10×4.0 mm 3  (length×width×thickness) prepared by injection moulding according to EN ISO 1873-2. 
     
     
       19. The multimodal polypropylene composition according to  claim 1 , wherein at least the second propylene homopolymer or random copolymer (W) is a propylene random copolymer. 
     
     
       20. The multimodal polypropylene composition according to  claim 1 , wherein both the first and the second propylene polymer (V) and (W) are propylene random copolymers. 
     
     
       21. An article, comprising the polypropylene composition according to  claim 1 .